Polyclonal antiharpin xoo rabbit antibody has been prepared successfully using purified harpin xoo protein as an immunogen. The ELISA titer of the antiserum against harpin xoo was about 1:2000. Western blot analysis showed that the antiserum could bind to the expression harpin xoo protein in particular. hrf1, encoding harpin xoo , is an expression in transgenic rice, detected by antiharpin xoo rabbit antibody. The rabbit antibody against harpin xoo can be used to study further about the biological function, harpin xoo localization, and hrf1 gene expression in other plants.